This invention relates to an apparatus for hydraulically transporting particulate solid material, such as coal, limestone, earth and sand, etc.
In the field of hydraulic transportation of particulate solid material, various apparatus are known in which a mixture of water and particulate material to be transported or a solid-liquid mixture is charged into at least one feed pipe fluidly connected to a transport pipe through a valve and the solid-liquid mixture charged in the feed pipe is forced by a high-pressure driving liquid into the transport pipe to hydraulically transport the particlate solid material to a predetermined destination. Such apparatus for hydraulically transporting particulate solid material which are sometimes referred to as hydrohoists are disclosed, for example, in U.S. Pat. Nos. 3,449,013; 3,556,682; 4,145,087; and 4,164,359.
In the technical field referred to hereinabove, there are some problems that have not yet been solved by the prior art. More specifically, the longer the distance covered by the solid-liquid mixture transported through the transport pipe, the higher becomes the flow velocity of the mixture at its central portion near the center axis of the transport pipe and the lower becomes the flow rate of the mixture at its peripheral portion remote from the center axis of the transport pipe and near the inner wall surface thereof. Owing to this phenomenon, the portion of the body of the mixture which is near the boundary between the mixture and the high-pressure driving liquid or the trailing end portion of the body of the mixture in the feed pipe is delayed in its flow, with a result that the solid particles in the trailing end portion of the body of the mixture remains in the feed pipe. The residual solid particles in the feed pipe tend to be incorporated in the driving liquid when the latter is returned to its reservoir. The present practice for preventing incorporation of the residual solid particles in the returning driving liquid is to cause the trailing end of the body of the mixture to flow out of a valve mounted between the feed pipe and the transport pipe before such valve is closed. This practice has a disadvantage in that the driving liquid is drawn into the mixture to lower the concentration of the latter and reduce transportation efficiency. Experiments have shown that the amount of the driving liquid drawn into the mixture is no less than 20% of the mixture.
To obviate these disadvantages of the prior art, proposals have been made to transport particulate solid material by keeping the same suspended in a mother liquid of slurry which has a specific gravity higher than that of the driving liquid and lower than that of the particulate solid material. By this means, the delay in the flow of the trailing end portion of the body of the mixture which would otherwise occur can be prevented. However, the problem of large solid particles (over 2 mm in grain size) falling to and deposited on the bottom of the transport pipe is raised when the concentration of the mother liquid of slurry is lowered by the driving liquid in the feed pipe.